Electrodes For Sleep Recordings Research Articles

Dopamine D2 receptors in the accumbal core region mediates the effects of fentanyl on sleep-wakefulness

Fentanyl, a potent analgesic and addictive substance, significantly impacts sleep-wakefulness (S-W). Acutely, it promotes wake, whereas chronic abuse leads to severe sleep disruptions, including insomnia, which contributes to opioid use disorders (OUD), a chronic brain disease characterized by compulsive opioid use and harmful consequences. Although the critical association between sleep disruptions and fentanyl addiction is acknowledged, the precise mechanisms through which fentanyl influences sleep remain elusive. Recent studies highlight the role of the dopaminergic system of the nucleus accumbens (NAc) in S-W regulation, but its specific involvement in mediating fentanyl’s effects on S-W remains unexplored. We hypothesized that dopamine D2 receptors mediate fentanyl-induced effects on S-W. To test this hypothesis, male C57BL/6J mice, instrumented with sleep recording electrodes and bilateral guide cannulas above the accumbal core region (NAcC), were utilized in this study. At dark onset, animals were bilaterally administered sulpiride (D2 receptors antagonist; 250 ng/side) in the NAcC followed by an intraperitoneal injection of fentanyl (1.2 mg/Kg). S-W was examined for the next 12 h. We found that systemic administration of fentanyl significantly increased wakefulness during the first 6 h of the dark which was followed by a significant increase in NREM and REM sleep during the second 6 h of the dark period. D2-receptor blockade significantly reduced this effect as evidenced by a significant reduction in fentanyl-induced wakefulness during first 6 h of dark period and sleep rebound during the second 6 h. Our findings suggest that D2 receptors in the NAcC plays a vital role in mediating the fentanyl-induced changes in S-W.

Ischemic Stroke Disrupts Sleep Homeostasis in Middle-Aged Mice.

Sleep disturbances, including insomnia and excessive daytime sleepiness, are highly prevalent in patients with ischemic stroke (IS), which severely impacts recovery and rehabilitation efforts. However, how IS induces sleep disturbances is unclear. Three experiments were performed on middle-aged C57BL/6J mice, instrumented with sleep recording electrodes and/or subjected to 1 h of middle cerebral artery (MCAO; Stroke group) or sham (Sham group) occlusion to induce IS. After 48 h of reperfusion (a) experiment 1 verified sensorimotor deficit (using Garcia scale) and infarction (using TTC staining) in this mouse model; (b) experiment 2 examined the effects of IS on the quality (sleep latency and NREM delta power) and quantity (duration) of sleep; and (c) experiment 3 determined the effects of IS on sleep homeostasis using sleep deprivation (SD) and recovery sleep (RS) paradigm. Stroke mice display (a) a significant correlation between sensorimotor deficit and cerebral infarction; (b) insomnia-like symptoms (increased sleep latency, reduced NREM duration and delta power) during the light (inactive) period and daytime sleepiness-like symptoms during the dark (active) period mimicking sleep in IS patients; and (c) impairments in the markers of sleep pressure (during SD) and sleep dissipation (during RS). Our results suggest that IS disrupts sleep homeostasis to cause sleep disturbances.

Early-life nicotine or cotinine exposure produces long-lasting sleep alterations and downregulation of hippocampal corticosteroid receptors in adult mice

Early-life exposure to environmental toxins like tobacco can permanently re-program body structure and function. Here, we investigated the long-term effects on mouse adult sleep phenotype exerted by early-life exposure to nicotine or to its principal metabolite, cotinine. Moreover, we investigated whether these effects occurred together with a reprogramming of the activity of the hippocampus, a key structure to coordinate the hormonal stress response. Adult male mice born from dams subjected to nicotine (NIC), cotinine (COT) or vehicle (CTRL) treatment in drinking water were implanted with electrodes for sleep recordings. NIC and COT mice spent significantly more time awake than CTRL mice at the transition between the rest (light) and the activity (dark) period. NIC and COT mice showed hippocampal glucocorticoid receptor (GR) downregulation compared to CTRL mice, and NIC mice also showed hippocampal mineralocorticoid receptor downregulation. Hippocampal GR expression significantly and inversely correlated with the amount of wakefulness at the light-to-dark transition, while no changes in DNA methylation were found. We demonstrated that early-life exposure to nicotine (and cotinine) concomitantly entails long-lasting reprogramming of hippocampal activity and sleep phenotype suggesting that the adult sleep phenotype may be modulated by events that occurred during that critical period of life.

001 Exploring the Orexin-tTA/TetO-DTA Mouse as a Model for Pediatric Narcolepsy

Abstract Introduction Narcolepsy is a sleep disorder caused by selective death of the orexin neurons that often begins in childhood. Orexin neuron loss disinhibits REM sleep during the active period and produces cataplexy, an abnormal behavioral state between REM sleep and wakefulness. Cataplexy is often more severe when narcolepsy develops in children compared to adults, but the mechanisms underlying this difference remain unknown. Methods We used orexin-tTA/TetO-DTA mice to model narcolepsy at different ages. When doxycycline is removed from the diet, the orexin neurons of these mice express diphtheria toxin A and die within 2–3 weeks. We removed doxycycline at 4 weeks (young-onset) or 14 weeks (adult-onset) of age in male and female mice. We implanted EEG and EMG electrodes for sleep recordings one week later and then recorded EEG/EMG/video for 24h at 3 and 13 weeks after removal of doxycycline. Age-matched controls had access to doxycycline diet for the entire experiment. Results Three weeks after doxycycline removal, both young-onset and adult-onset mice developed cataplexy and the sleep-wake fragmentation characteristic of narcolepsy. Age of orexin cell loss did not significantly affect cataplexy severity, however, female mice had more cataplexy than male mice overall. Both young- and adult-onset mice showed a 99% loss of orexin neurons at 3 weeks. Conclusion Considered together, our results suggest that the orexin-tTA/TetO-DTA mouse model of narcolepsy does not capture the severe cataplexy that is often seen in the human pediatric population. Support (if any):

The Impacts of Age and Sex in a Mouse Model of Childhood Narcolepsy.

Narcolepsy is a sleep disorder caused by selective death of the orexin neurons that often begins in childhood. Orexin neuron loss disinhibits REM sleep during the active period and produces cataplexy, episodes of paralysis during wakefulness. Cataplexy is often worse when narcolepsy develops in children compared to adults, but the reason for this difference remains unknown. We used orexin-tTA; TetO DTA mice to model narcolepsy at different ages. When doxycycline is removed from the diet, the orexin neurons of these mice express diphtheria toxin A and die within 2–3 weeks. We removed doxycycline at 4 weeks (young-onset) or 14 weeks (adult-onset) of age in male and female mice. We implanted electroencephalography (EEG) and electromyography (EMG) electrodes for sleep recordings two weeks later and then recorded EEG/EMG/video for 24 h at 3 and 13 weeks after removal of doxycycline. Age-matched controls had access to doxycycline diet for the entire experiment. Three weeks after doxycycline removal, both young-onset and adult-onset mice developed severe cataplexy and the sleep-wake fragmentation characteristic of narcolepsy. Cataplexy and maintenance of wake were no worse in young-onset compared to adult-onset mice, but female mice had more bouts of cataplexy than males. Orexin neuron loss was similarly rapid in both young- and adult-onset mice. As age of orexin neuron loss does not impact the severity of narcolepsy symptoms in mice, the worse symptoms in children with narcolepsy may be due to more rapid orexin neuron loss than in adults.

Rats exposed to chronic alcohol display protracted insomnia and daytime sleepiness-like behavior during alcohol withdrawal✰

Alcohol use disorder (AUD), a chronic brain disorder, is characterized by a multitude of symptoms, including insomnia, during withdrawal. Previously, we have shown that rats exposed to chronic alcohol displayed insomnia-like symptoms during acute withdrawal. Since insomnia lasts for several years and is a major risk factor of relapse to alcoholism, the present study is designed to investigate the long-term effects of alcohol withdrawal on sleep-wakefulness. Adult male Sprague-Dawley rats, instrumented with sleep recording electrodes, were divided into two groups: Alcohol and Control. Rats were either administered alcohol (35% v/v), mixed with infant formula (Alcohol group) or control mixture containing water and infant formula (Controls; 10mL/kg) every 8h for 4 days using Majchrowicz's chronic binge drinking protocol. Electrographic recordings of sleep-wakefulness were performed until withdrawal day 7, however, the data was analyzed for withdrawal days 3, 5 and 7 in both Control and Alcohol groups. As compared to the controls, alcohol-exposed rats displayed insomnia-like symptoms as revealed by a) significant reduction in the quantity and quality of sleep during the light (inactive) period and b) a significant increase in NREM sleep with a concomitant reduction in the amount of time spent in the wakefulness during the dark (active) period of alcohol withdrawal. Our results suggest that the chronic binge model of alcohol dependence mimics clinical symptoms of AUD especially protracted insomnia and is suitable for understanding the mechanisms associated with alcohol withdrawal-induced behaviors.

Melatonin promotes sleep in mice by inhibiting orexin neurons in the perifornical lateral hypothalamus.

Melatonin promotes sleep. However, the underlying mechanisms are unknown. Orexin neurons in the perifornical lateral hypothalamus (PFH) are pivotal for wake promotion. Does melatonin promote sleep by inhibiting orexin neurons? We used C57BL/6J mice and designed 4 experiments to address this question. Experiment 1 used double-labeled immunofluorescence and examined the presence of melatonin receptors on orexin neurons. Second, mice, implanted with bilateral guides targeted toward PFH and sleep-recording electrodes, were infused with melatonin (500pmole/50nL/side) at dark onset (onset of active period), and spontaneous bouts of sleep-wakefulness were examined. Third, mice, implanted with bilateral guides into the PFH, were infused with melatonin (500pmole/50nL/side) at dark onset and euthanized 2hours later, to examine the activation of orexin neurons using c-Fos expression in orexin neurons. Fourth, mice, implanted with PFH bilateral guides and sleep-recording electrodes, were infused with melatonin receptor antagonist, luzindole (10pmol/50nL/side), at light onset (onset of sleep period), and spontaneous bouts of sleep-wakefulness were examined. Our results suggest that orexin neurons express MT1, but not MT2 receptors. Melatonin infusion into the PFH, at dark onset, site-specifically and significantly increased NREM sleep (43.7%, P=.003) and reduced wakefulness (12.3%, P=.013). Local melatonin infusion at dark onset inhibited orexin neurons as evident by a significant reduction (66%, P=.0004) in the number of orexin neurons expressing c-Fos. Finally, luzindole infusion-induced blockade of melatonin receptors in PFH at sleep onset significantly increased wakefulness (44.1%, P=.015). Based on these results, we suggest that melatonin may act via the MT1 receptors to inhibit orexin neurons and promote sleep.

Lesion of the basal forebrain cholinergic neurons attenuates sleepiness and adenosine after alcohol consumption.

Alcohol has a profound effect on sleep. However, neuronal substrates mediating sleep-promoting effects of alcohol are unknown. Since the basal forebrain (BF) cholinergic neurons are implicated in the homeostatic regulation of sleep, we hypothesized that the BF cholinergic neurons may have an important role in sleepiness observed after alcohol consumption. 192-IgG-saporin (bilateral BF infusions) was used to selectively lesion BF cholinergic neurons in adult male Sprague-Dawley rats. Standard surgical procedures were used to implant sleep recording electrodes or microdialysis guide cannulas. The first experiment used between-group design [lesion and sham (controls)] and examined effects of BF cholinergic neuronal lesions on alcohol (3g/Kg; ig) induced sleep promotion. The second experiment used within-group design [lesion (ipsilateral BF) and sham (controls; contralateral BF) in same animal] and local reverse microdialysis infusion of alcohol (300mM) to examine the effects of cholinergic neuronal lesions on extracellular adenosine in the BF. Alcohol had a robust sleep promoting effect in controls as evidenced by a significant reduction in sleep onset latency and wakefulness; non-rapid eye movement sleep was significantly increased. No such alcohol-induced sleep promotion was observed in lesioned rats with significantly fewer BF cholinergic neurons. Rapid eye movement sleep was minimally affected. Adenosine release was significantly reduced following local infusion of alcohol on the lesion side, with significantly fewer cholinergic neurons as compared with the control side. Based on these results, we suggest that alcohol promotes sleep by increasing extracellular adenosine via its action on cholinergic neurons of the BF. Read the Editorial Highlight for this article on page 620.

The high-frequency component of heart rate variability during extended wakefulness is closely associated with the depth of the ensuing sleep in C57BL6 mice

This study aimed to test the hypothesis that, during extended wakefulness, parasympathetic activity is associated with the depth of the subsequent recovery sleep in mice. Fourteen male C57BL/6 mice were implanted with electrodes for sleep recording. Continuous spectral analysis was performed on the electroencephalogram (EEG) to obtain theta power (6–9Hz) and delta power (0–4Hz), as well as the R-R interval signals in order to quantify the high-frequency power (HF) and normalized low-frequency power (LF%) that are used to assess parasympathetic and sympathetic activity, respectively. All animals underwent a sleep deprivation experiment and a control experiment (6-h intervention and 1-h recovery period) on two separate days. During sleep deprivation, HF and theta power during wakefulness were significantly higher than during the control wakefulness after the second hour and first hour, respectively. During recovery non-rapid eye movement sleep, there was a rebound in sleep time and delta power as well as an elevation in HF relative to control post-intervention sleep. Both the rise in HF and theta power during extended wakefulness were found to be positively correlated with the delta power rebound. Furthermore, the HF change during extended wakefulness was also correlated with the amount of sleep loss and the enhancement of waking theta power. Our finding suggests that waking parasympathetic activity intimately reflects the cumulative sleep pressure, suggesting a potential role to be an autonomic marker for sleep propensity.

High-amplitude theta wave bursts characterizing narcoleptic mice and patients are also produced by histamine deficiency in mice.

Histamine and orexins are wake promoters released by hypothalamic neurons. The activity of histamine neurons is increased by orexin neurons. Recently, it has been shown that orexin deficiency entails high-amplitude theta wave bursts during rapid eye movement sleep and cataplexy in narcoleptic mice. The primary aim of this study was to assess whether histamine system is involved in high-amplitude theta wave burst generation during rapid eye movement sleep. The secondary aim was to assess the effects of combined histamine and orexin deficiency on high-amplitude theta wave bursts during rapid eye movement sleep in mice. Twelve histidine-decarboxylase knockout mice with congenital histamine deficiency, seven double mutant mice with combined deficiency of orexin neurons and histamine, and 11 wild-type control mice were studied with electrodes for sleep recordings and a telemetric blood pressure transducer. High-amplitude theta wave bursts during rapid eye movement sleep were detected in each of the histidine-decarboxylase knockout and double mutant mice, whereas only one burst was found in a wild-type control mouse. High-amplitude theta wave bursts occurred significantly more often and were significantly longer in double mutant than in histidine-decarboxylase knockout mice. In conclusion, it was demonstrated that, similarly to orexin, the chronic impairment of histamine entailed high-amplitude theta wave bursts during rapid eye movement sleep. The current data also suggested a synergistic role of orexin and histamine signalling on high-amplitude theta wave bursts during rapid eye movement sleep in mice.

Nicotine administration in the wake-promoting basal forebrain attenuates sleep-promoting effects of alcohol.

Nicotine and alcohol co-abuse is highly prevalent, although the underlying causes are unclear. It has been suggested that nicotine enhances pleasurable effects of alcohol while reducing aversive effects. Recently, we reported that nicotine acts via the basal forebrain (BF) to activate nucleus accumbens and increase alcohol consumption. Does nicotine suppress alcohol-induced aversive effects via the BF? We hypothesized that nicotine may act via the BF to suppress sleep-promoting effects of alcohol. To test this hypothesis, adult male Sprague-Dawley rats were implanted with sleep-recording electrodes and bilateral guides targeted toward the BF. Nicotine (75 pmol/500 nL/side) or artificial cerebrospinal fluid (ACSF; 500 nL/side) was microinjected into the BF followed by intragastric alcohol (ACSF + EtOH and NiC + EtOH groups; 3 g/kg) or water (NiC + W and ACSF + W groups; 10 mL/kg) administration. On completion, rats were killed and processed to localize injection sites in the BF. The statistical analysis revealed a significant effect of treatment on sleep-wakefulness. While rats exposed to alcohol (ACSF + EtOH) displayed strong sleep promotion, nicotine pre-treatment in the BF (NiC + EtOH) attenuated alcohol-induced sleep and normalized sleep-wakefulness. These results suggest that nicotine acts via the BF to suppress the aversive, sleep-promoting effects of alcohol, further supporting the role of BF in alcohol-nicotine co-use.

Baclofen and gamma-hydroxybutyrate differentially altered behavior, EEG activity and sleep in rats

Objectives: Animal and human studies have shown that sleep may have an impact on functional recovery after brain damage. Baclofen (Bac) and gamma-hydroxybutyrate (GHB) have been shown to induce physiological sleep in humans, however, their effects in rodents are unclear. The aim of this study is to characterize sleep and electroencelphalogram (EEG) after Bac and GHB administration in rats. We hypothesized that both drugs would induce physiological sleep.Methods: Adult male Sprague-Dawley rats were implanted with EEG/electromyogram (EMG) electrodes for sleep recordings. Bac (10 or 20mg/kg), GHB (150 or 300mg/kg) or saline were injected 1h after light and dark onset to evaluate time of day effect of the drugs. Vigilance states and EEG spectra were quantified.Results: Bac and GHB induced a non-physiological state characterized by atypical behavior and an abnormal EEG pattern. After termination of this state, Bac was found to increase the duration of non-rapid eye movement (NREM) and rapid eye movement (REM) sleep (∼90 and 10min, respectively), reduce sleep fragmentation and affect NREM sleep episode frequency and duration (p<0.05). GHB had no major effect on vigilance states. Bac drastically increased EEG power density in NREM sleep in the frequencies 1.5–6.5 and 9.5–21.5Hz compared to saline (p<0.05), while GHB enhanced power in the 1–5-Hz frequency band and reduced it in the 7–9-Hz band. Slow-wave activity in NREM sleep was enhanced 1.5–3-fold during the first 1–2h following termination of the non-physiological state. The magnitude of drug effects was stronger during the dark phase.Conclusion: While both Bac and GHB induced a non-physiological resting state, only Bac facilitated and consolidated sleep, and promoted EEG delta oscillations thereafter. Hence, Bac can be considered a sleep-promoting drug and its effects on functional recovery after stroke can be evaluated both in humans and rats.

Acute binge alcohol administration reverses sleep-wake cycle in Sprague Dawley rats.

Binge alcohol drinking is among the most common pattern of alcohol consumption in our society. Binge alcohol consumption has serious negative consequence on mental and physical health. Although alcohol consumption is known to have profound impact on sleep, it is yet unknown as to how binge alcohol affects/alters sleep-wakefulness. The objective of this study was to examine the effect of acute binge alcohol administration on sleep-wakefulness. Male Sprague Dawley rats were used in the study. Under standard aseptic surgical conditions, rats (N = 7) were implanted with sleep-recording electrodes. After postoperative recovery and habituation, baseline sleep-wakefulness was recorded. Subsequently, rats were exposed to binge alcohol treatment as follows: One hour before light onset, a priming dose of 5 g/kg of alcohol was administered followed by 2 subsequent doses (adjusted based on the intoxication level of the rat) approximately 8 hours apart. Sleep-wakefulness was continuously recorded for 3 days post-binge. Acute binge alcohol administration had no significant effect on sleep-wakefulness on post-binge Day 1. However, on post-binge Day 2, after blood alcohol concentration (BAC) was 0, sleep disruptions were observed manifested by a reversal of sleep-wakefulness as evident from insomnia-like symptoms (significant increase in wakefulness; significant reduction in nonrapid eye movement [NREM] sleep) during the normal sleep (light) period and excessive sleep (significant increase in NREM sleep) during the normal active (dark) period similar to excessive daytime sleepiness in humans. All sleep-wakefulness changes were normalized on Day 3 post-binge. Alcohol hangover is defined as the presence of unpleasant symptoms that peak when BAC is 0. Our results suggest that the reversal of sleep-wakefulness accompanies alcohol hangover after binge alcohol administration.

Sleep deprivation reduces neuroglobin immunoreactivity in the rat brain

Neuroglobin (Ngb), a protein located in the mammal's brain, is involved in oxygen transport and free radical scavenging inside the neurons. Ngb colocalizes with choline acetyltransferase in the laterodorsal tegmental nucleus and in the pontine tegmental nucleus, both involved in the sleep-wake cycle regulation. Some studies have shown that free radicals accumulated during prolonged wakefulness are removed during sleep. Therefore, Ngb could act as a regulator of free radicals generated during prolonged wakefulness in the brain. The aim of this study was to determine whether prolonged wakefulness affects Ngb immunoreactivity because of increases in the oxidative stress induced by continuous neuronal activity. For this purpose, male adult Wistar rats were implanted with electrodes for sleep recordings and were divided into control and sleep-deprived groups. Sleep deprivation was carried out for 24 h by gentle handling of the animals. Sleep-wake activity was determined during the deprivation period or 24 h of control conditions. Subsequently, both groups of animals were killed and their brains were obtained and processed for Ngb immunohistochemical analysis and detection of lipid peroxidation. Our data found no evidence of increased oxidative stress in the brains of sleep-deprived animals compared with the controls. The number of Ngb-positive cells was decreased in the sleep-deprived animals in all analyzed areas of the brain compared with the control group. Our results suggest that Ngb could be involved in sleep regulation, independent of its role in the control of oxidative stress.

Metabolic effects of chronic sleep restriction in rats.

Chronic partial sleep loss is associated with obesity and metabolic syndrome in humans. We used rats with lesions in the ventrolateral preoptic area (VLPO), which spontaneously sleep about 30% less than intact rats, as an animal model to study the consequences of chronic partial sleep loss on energy metabolism. Adult male Sprague-Dawley rats (300-365 g). We ablated the VLPO in rats using orexin-B-saporin and instrumented them with electrodes for sleep recordings. We monitored their food intake and body weight for the next 60 days and assessed their sleep-wake by 24-h EEG/EMG recordings on day 20 and day 50 post-surgery. On day 60, after blood samples were collected for metabolic profiling, the animals were euthanized and the brains were harvested for histological confirmation of the lesion site. VLPO-lesioned animals slept up to 40% less than sham-lesioned rats. However, they showed slower weight gain than sham-lesioned controls, despite having normal food intake. An increase in plasma ghrelin and a decrease in leptin levels were observed, whereas plasma insulin levels remained unaffected. As expected from leaner animals, plasma levels of glucose, cholesterol, triglycerides, and C-reactive protein were reduced in VLPO-lesioned animals. Chronic partial sleep loss did not lead to obesity or metabolic syndrome in rats. This finding raises the question whether adverse metabolic outcomes associated with chronic partial sleep loss in humans may be due to factors other than short sleep, such as circadian disruption, inactivity, or diet during the additional waking hours.

Control of cardiovascular variability during undisturbed wake-sleep behavior in hypocretin-deficient mice

The central neural mechanisms underlying differences in cardiovascular variability between wakefulness, non-rapid-eye-movement sleep (NREMS), and rapid-eye-movement sleep (REMS) remain poorly understood. These mechanisms may involve hypocretin (HCRT)/orexin signaling. HCRT signaling is linked to wake-sleep states, involved in central autonomic control, and impaired in narcoleptic patients. Thus, we investigated whether HCRT signaling plays a role in controlling cardiovascular variability during spontaneous behavior in HCRT-deficient mice. HCRT-ataxin3 transgenic mice lacking HCRT neurons (TG), knockout mice lacking HCRT peptides (KO), and wild-type controls (WT) were instrumented with electrodes for sleep recordings and a telemetric blood pressure transducer. Fluctuations of systolic blood pressure (SBP) and heart period (HP) during undisturbed wake-sleep behavior were analyzed with the sequence technique, cross-correlation functions, and coherent averaging of SBP surges. During NREMS, all mice had lower SBP variability, greater baroreflex contribution to HP control at low frequencies, and greater amplitude of the central autonomic and baroreflex changes in HP associated with SBP surges than during wakefulness. During REMS, all mice had higher SBP variability and depressed central autonomic and baroreflex HP controls relative to NREMS. HP variability during REMS was higher than during NREMS in WT only. TG and KO also had lower amplitude of the cardiac baroreflex response to SBP surges during REMS than WT. These results indicate that chronic lack of HCRT signaling may cause subtle alterations in the control of HP during spontaneous behavior. Conversely, the integrity of HCRT signaling is not necessary for the occurrence of physiological sleep-dependent changes in SBP variability.

High‐amplitude theta wave bursts during REM sleep and cataplexy in hypocretin‐deficient narcoleptic mice

Neurons that release hypocretin (HCRT; orexin) peptides control wake-sleep states and autonomic functions, and are lost in patients with narcolepsy with cataplexy. Bursts of high-amplitude electroencephalographic (EEG) activity have been reported during behavioural arrests and rapid eye movement sleep (REMS) episodes at sleep onset in HCRT-deficient narcoleptic mice. Quantitative information on these EEG phenomena is lacking. We aimed to quantify EEG frequency, occurrence rate, daily rhythm and cardiovascular correlates of high-amplitude EEG bursts during REMS and cataplexy. Twenty HCRT-deficient mice and 15 congenic wild-type controls were instrumented with electrodes for sleep recordings and a telemetric blood pressure transducer. Short (1-2 s) high-amplitude bursts of pointed theta waves (7 Hz) occurred during either REMS or cataplexy in 80% of HCRT-deficient mice without any significant accompanying modification in systolic blood pressure or heart period. Theta bursts were significantly more likely to occur during the dark period and in the last third of REMS episodes. Similar EEG events were detected in a significantly lower fraction (27%) of wild-type mice and with a significantly lower occurrence rate (0.8 versus 5 per hour of REMS). These data demonstrate that occurrence of high-amplitude theta bursts is facilitated during REMS and cataplexy in narcoleptic mice. Analysis of EEG frequency and daily and intra-episode patterns of event occurrence do not support interpretation of theta bursts as temporally displaced pre-REMS spindles. Facilitation of high-amplitude theta bursts may thus represent a novel neurophysiological abnormality associated with chronic HCRT deficiency.

Sleep Related Changes in Blood Pressure in Hypocretin-Deficient Narcoleptic Mice

Although blood pressure during sleep and the difference in blood pressure between sleep and wakefulness carry prognostic information, little is known on their central neural mechanisms. Hypothalamic neurons releasing hypocretin (orexin) peptides control wake-sleep behavior and autonomic functions and are lost in narcolepsy-cataplexy. We investigated whether chronic lack of hypocretin signaling alters blood pressure during sleep. Comparison of blood pressure as a function of the wake-sleep behavior between 2 different hypocretin-deficient mouse models and control mice with the same genetic background. N/A. Hypocretin-ataxin3 transgenic mice with genetic ablation of hypocretin neurons (TG, n = 12); hypocretin gene knock-out mice (KO, n = 8); congenic wild-type controls (WT, n = 10). Instrumentation with electrodes for sleep recordings and a telemetric blood pressure transducer. Blood pressure was significantly higher in either TG or KO than in WT during non-rapid eye movement sleep (NREMS; 4 ± 2 and 7 ± 2 mm Hg, respectively) and rapid eye movement sleep (REMS; 11 ± 2 and 12 ± 3 mm Hg, respectively), whereas it did not differ significantly between groups during wakefulness. Accordingly, the decrease in blood pressure between either NREMS or REMS and wakefulness was significantly blunted in TG and KO with respect to WT. Chronic lack of hypocretin signaling may entail consequences on blood pressure that are potentially adverse and that vary widely among wake-sleep states.

Sleep–wakefulness in alcohol preferring and non-preferring rats following binge alcohol administration

The alcohol-preferring (P) rat is a valid animal model of alcoholism. However, the effect of alcohol on sleep in P or alcohol non-preferring (NP) rats is unknown. Since alcohol consumption has tremendous impact on sleep, the present study compared the effects of binge alcohol administration on sleep–wakefulness in P and NP rats. Using standard surgical procedures, the P and NP rats were bilaterally implanted with sleep recording electrodes. Following post-operative recovery and habituation, pre-ethanol (baseline) sleep–wakefulness was electrographically recorded for 48 h. Subsequently, ethanol was administered beginning with a priming dose of 5 g/Kg followed by two doses of 2 g/Kg every 8 h on the first day and three doses of 3 g/Kg/8 h on the second day. On the following day (post-ethanol), undisturbed sleep–wakefulness was electrographically recorded for 24 h. Our initial results suggest that, during baseline conditions, the time spent in each of the three behavioral states: wakefulness, non-rapid eye movement (NREM) sleep and REM sleep, was comparable between P and NP rats. However, the P rats were more susceptible to changes in sleep–wakefulness following 2 days of binge ethanol treatment. As compared to NP rats, the P rats displayed insomnia like symptoms including a significant reduction in the amount of time spent in NREM sleep coupled with a significant increase in wakefulness on post-ethanol day. Subsequent analysis revealed that binge ethanol induced increased wakefulness and reduced NREM sleep in P rats occurred mainly in the dark period. This is the first study that: (1) demonstrates spontaneous sleep–wake profile in P and NP rats, and (2) compares the effects of binge ethanol treatment on sleep in P and NP rats. Our results suggest that, as compared to NP rats, the P rats were more susceptible to sleep disruptions after binge ethanol treatment. In addition, the P rats exhibited insomnia-like symptoms observed during abstinence from alcohol in human subjects.

Dysregulation of Heart Rhythm During Sleep in Leptin-Deficient Obese Mice

sleep deeply affects cardiac autonomic control, the impairment of which is associated with cardiovascular mortality. Obesity entails increased cardiovascular risk and derangements in sleep and cardiac autonomic control. We investigated whether cardiac autonomic control is impaired during sleep in ob/ob mice with morbid obesity caused by congenital leptin deficiency. indexes of cardiac autonomic control based on spontaneous cardiovascular fluctuations were compared between ob/ob and lean wild-type (+/+) mice during wakefulness, non-rapid eye movement sleep (NREMS), and rapid eye movement sleep (REMS). N/A PATIENTS OR PARTICIPANTS: 7 ob/ob and 11 +/+ male mice. instrumentation with electrodes for sleep recordings and a telemetric transducer for measuring blood pressure and heart period. In ob/ob mice, the variability of heart period and cardiac baroreflex sensitivity (sequence technique) were significantly lower than in +/+ mice during each wake-sleep state. The vagal modulation of heart period was significantly weaker in ob/ob than in +/+ mice during NREMS and REMS. In ob/ob mice, the cross-correlation function between heart period and blood pressure suggested that the baroreflex contribution to cardiac control was lower than in +/+ mice during wakefulness and NREMS, whereas the contribution of central autonomic commands was lower than in +/+ mice during NREMS and REMS. These data indicate a dysregulation of cardiac autonomic control during sleep in ob/ob mice. Ob/ob mice may represent a useful tool to understand the molecular pathways that lead to cardiac autonomic dysregulation during sleep in obesity.